Review and evaluation of commercially available wound dressings

Wound dressings are materials applied to wounds to promote healing, preventing infection and protecting from further injury. Depending on the application, they are available in many forms and types, each with various functions [1]. The primary purpose of a dressing is to create an environment that promotes wound healing, supports healthy cell growth, and facilitates the healing process (Fig. 1) [2]. The frequency of dressing changes depends on the specific condition of the wound, particularly the amount of exudate relative to the dressing's absorbent capacity, with changes typically occurring between 1 day and 1 week [3].

Fig. 1.

Wound healing process with an adequately fitted dressing. (figure based on [4])

Fig. 2

Prospects for the global dressing market (figure based on [5])

More than 3,000 different types of wound dressings are currently available on the market. The wound dressing market is a significant and rapidly growing sector within the medical device industry, essential for effectively treating wounds from various sources. The global wound dressing industry is projected to reach a revenue of approximately US$ 18,867.4 million by 2030 [5].

Despite the vast range of dressings available on the market and the many possible applications, researchers are still working on the next generation [6,7,8]. Efforts are being made to make dressings enhance the wound closure process, responding to stimuli such as pH and temperature. In addition, researchers are working on wound dressings with better mechanical properties that could be applied to moving, bending or stretching areas on the human body - neck, elbows or knees. Another group of smart dressings focuses on monitoring parameters such as pH, temperature or glucose levels and signalling a change in these parameters, which indicates wound infection [9].

One other group of smart wound dressings are those designed to deliver medications. These dressings use different types of medication depending on the patient's needs. These may include antibiotics [10] and metformin [11]. However, the Polish Wound Management Association does not recommend using antibiotics in topical applications to wounds [12]. In order to avoid overuse of antibiotics or antibiotic resistance, nanoparticles can be used. Metal nanoparticles such as silver [13], copper [14], zinc [15] and gold [16] are the most frequently used. In addition to dressings made from conventional biomaterials containing commonly used additives, research is being carried out on dressings containing soft electronic materials that collect data from the wound and transmit them to a smartphone [17,18].

A separate group of smart dressings are those made using 3D printing technology. This technology enables the design of dressings to be customised to the patient's specific needs. In addition, 3D bioprinting allows the incorporation of drugs or other active substances into the dressing material, promoting wound healing [19,20].

A broad group of dressing materials can be classified by considering various criteria such as function, type of raw material, and material form (Tab. 1). The raw materials used for typical dressing materials are cotton, cellulose fibres, alginates, polyamides, polyurethanes or other synthetic polymers [21,22]. Dressings can also take various forms, such as films, non-wovens, foams, hydrogels, hydrocolloids, or meshes [23,24].

The proper choice of dressing can and should have a significant and crucial impact on wound healing. It should be carried out based on a comprehensive wound assessment following the latest guidelines and trends, patient preferences, wound healing history and additional factors (e.g. diseases) affecting the healing process.

Wound healing is a particular biological process that is linked to physiological parameters. It consists of the following phases [26]: –

Haemostasis is the first stage of wound healing, during which a temporary fibrin matrix of the wound is produced, and platelets release cytokines and growth factors in the wound.

Remodelling is the final stage of wound healing; there is a reduction in the density of fibroblasts and capillaries, and the initial scar tissue is removed and replaced by ECM, which more closely resembles healthy skin. The new tissue gradually becomes stronger and more elastic.

In 2004, in Paris, at the Congress of the European Wound Management Associations (EWMA), medical experts (International Advisory Board) published the TIME wound treatment concept for doctors and therapists involved in wound care [27]. It addresses the different phases of wound healing, describes them practically, and defines goals and actions specific to each stage.

In 2019, the TIME concept was updated by two more factors: repair/regeneration (R) and social (S) [28] (Fig. 3). Factor R focuses on promoting wound closure, among others, by stimulating cell activity. Factor S emphasises the importance of social and patient-related factors. Understanding these overarching factors is crucial for effective wound management.

Fig. 3.

TIMERS concept (figure based on [29])

This study showed the results of free swell absorptive capacity, the moisture vapour transmission rate and mechanical analysis of commercially available dressings from various manufacturers. So far, there has been no collective analysis of dressings from different groups and multiple manufacturers. Dressings were divided into groups and presented as the average results for a given group. The EN 13726 standard describes the test methods recommended for assessing the moisture vapour transmission rate and free swell absorptive capacity. However, it does not specify values for these parameters in a way that would allow the categorisation of dressings.

The following tests of dressing were performed: –

The free swell absorptive capacity was determined according to the guidelines described in EN 13726-1:2002/AC:2003 [30] (Fig. 4).

Fig. 4.

Scheme of free swell absorptive capacity (figure based on self-analysis)

Fig. 5.

Scheme of moisture vapour transmission rate (figure based on self-analysis)

Studies were conducted on the following groups of dressings: –

Hydrogel dressings (Fig. 6) are designed to maintain an optimal moisture balance in the wound [33]. They are typically used for painful, dry wounds, burns, radiation-induced skin injuries, and severe lacerations. These dressings are non-adherent, meaning they do not damage newly formed tissue and help reduce pain. However, they are unsuitable for heavily exudating wounds and may require an additional dressing to secure them.

Fig. 6.

Mode of action of the hydrogel dressing in the case of- a) dry wounds, b) wounds with exudate (figure based on [34])

Fig. 7.

Mode of action of the hydrocolloid dressing (figure based on self-analysis)

Fig. 8

Mode of action of the a) super absorption dressing and b) superabsorbent polymer (figure based on [36])

The dressings used in this study are Zetuvit^® Plus (Hartmann), Mextra Superabsorbent^® (Mölnlycke), Vliwasorb^® Pro (Lohmann & Rauscher), Eclypse Adherent (Advancis Medica), Vliwasorb^® Adhesive (Lohmann & Rauscher), HydroClean^® Plus (Hartmann), Sorbact^® Superabsorbent (Abigo Medical), and ConvaMax™ Superabsorber (Convatec). –

Absorbent dressings (Fig. 9) can absorb wound exudate and provide a relatively dry wound environment. They are characterised by varying degrees of absorbency, depending on the nature of the wound. They absorb moisture from the wound by encapsulating it within their structure, and the dressing layer directly adhering to the wound remains dry, preventing skin maceration and soaking of the dressing.

Fig. 9.

Mode of action of the absorption dressing (figure based on self-analysis)

Dressings used for this research are Vliwaktiv^® (Lohmann & Rauscher), Elastopor Steril (Zarys), Sorbact^® Absorption Dressing (Abigo Medical), Biatain^® Super Adhesive (Coloplast), and Vliwazell^® (Lohmann & Rauscher). –

Calcium alginate dressings (Fig. 10) are highly absorbent fibrous structures [37]. Due to the sorptive capacity of alginate, a gel is formed when in contact with the exudate, which promotes autolytic cleansing of the wound while absorbing excess fluid, helping to accelerate the wound healing process. They are suitable for wounds that generate moderate to profuse exudate and require additional support to keep them in place. They can be changed daily, depending on the amount of exudate in the wound.

Fig. 10.

Mode of action of the alginate dressing (figure based on self-analysis)

Dressings used for this research are Sorbalgon^® (Hartmann), Medisorb A (TZMO), Kaltostat™ (Convatec), and Suprasorb^® A (Lohmann & Rauscher). –

Foam dressings (Fig. 11) aim to create a moist environment that promotes wound healing. They are made of water-resistant polymers, usually polyurethane, and absorb moderate amounts of exudate. They tend not to adhere tightly and permit vapour transmission, but at the same time, prevent the penetration of bacteria and other contaminants into the wound.

Fig. 11.

Mode of action of the foam dressing (figure based on self-analysis)

Dressings used for this research are Medisorb P Plus Adhesive (TZMO), Mepilex^® Border EM (Mölnlycke), Mepilex^® EM (Mölnlycke), Mepilex^® Border (Mölnlycke), Aquacel™ Foam (Convatec), Aquacel™ Foam Non Adhesive (Convatec), Allevyn Adhesive (Smith & Nephew), Foam Lite™ Convatec (Convatec), Biatain^® Non Adhesive (Coloplast), Sorbact^® Foam (Abigo Medical), Suprasorb^® P (Lohmann & Rauscher), Suprasorb^® P Sensitive Border (Lohmann & Rauscher), HydroTac (Hartmann), and HydroTac^® Transparent Comfort (Hartmann).

The moisture vapour transmission rate (MVTR) is crucial for evaluating dressings. The higher the MVTR value, the greater the dressing's ability to transmit water vapour. For the dressings tested in this study, the MVTR values ranged from 76 to 6,100 g/m²/24h, depending on the group (Fig. 12). The higher the moisture vapour transmission rate (MVTR), the more breathable and permeable the dressing is.

Fig. 12.

Moisture vapour transmission rate (MVTR) of wound dressing when in contact with vapour

The highest MVTR values were reported for the hydrogel, absorbent and alginate dressings, where values exceeded 3,000 (g/m²/24h). Hydrogel dressings can absorb liquid and then subsequently release it from their structure as vapour. The absorbent dressings can absorb moisture vapour but partially retain it in their structure. Alginate dressings are based on alginate, which has absorbent properties. The lowest value of MVTR was reported for occlusive hydrocolloids [38], which do not allow water, oxygen, or bacteria into the wound. It can be explained by the waterproof barrier on the dressing. Therefore, hydrocolloids should not be placed on heavily exuding wounds due to the risk of maceration. Because of their porous structure [39], foam dressings have the capability to retain moisture vapour and consequently create a moist wound healing environment.

The results of free swell absorptive capacity are shown in Figure 13. The highest value was reported for superabsorbent and absorbent dressings, while hydrocolloids had the lowest free swell absorptive capacity value.

Fig. 13.

Free swell absorptive capacity of dressings

The free swell absorptive capacity results are closely related to the structure and material of the individual dressings. Since superabsorbent dressings contain SAP, they can absorb liquids by multiples of their weight [40]. Absorbent dressings are composed of several layers, significantly increasing their absorptive capacity. Foam dressings, which absorb liquid relatively efficiently, are characterised by a highly porous structure, favouring their ability to absorb fluid. Hydrogels are made of hydrophilic polymers, contributing to their relatively good absorption capacity. When exposed to the cations contained in the absorbed fluids, alginate dressings undergo a gelation process, which limits their ability to absorb fluids. Hydrocolloid dressings, however, absorb only a tiny amount of fluid to produce a gel that will provide a sufficiently moist wound environment.

Table 2 shows the mechanical properties of the dressings. The maximum strength and tensile strength were defined, allowing the elasticity of the dressing to be determined. Elasticity is essential in providing patients with freedom of movement [41].

Hydrocolloid dressings have the highest elongation value in both directions. The reason for this is their structure - the inner layer is made of hydrocolloids, while the outer layer is made of polyurethane foam or film – which allows them to be used in hard-to-treat areas such as elbows, heels or knees. Hydrogel dressings are known for their poor mechanical properties, while their relatively high elongation at maximum strength is worth mentioning. They are designed to be applied and removed delicately to minimise further skin trauma [42]. They should equally exhibit mechanical and physical properties similar to the extracellular matrix of human skin [43]. Foam dressings are similarly flexible, as confirmed by the study results. However, by having to provide a cushioning effect on the wound, they are thicker than hydrogel and hydrocolloid dressings [44]. Absorbent and superabsorbent dressings have mechanical properties based on their layered structure - a layer that adheres to the wound, a distribution layer, an absorbent layer and an outer layer that limits their elasticity. In contrast, the dressings with the lowest elongation values are alginate dressings, which are most commonly non-woven. In addition to their good sorptive properties, calcium alginate fibres have relatively low strength properties (14–18 cN/tex) and low elongation values (2–6%) [45].

This study characterises the critical properties of various commercially available wound dressings. The EN 13726 standard outlines the recommended test methods for assessing the moisture vapour transmission rate and free swell absorptive capacity. However, it does not provide specific values for these parameters that would allow for the categorisation of dressings. The commercially available dressings vary significantly, and their different structures (e.g., gels, foams, absorbents) can substantially impact the healing process of different types of wounds. Our research confirms the influence of dressing structure on absorption capacity, elasticity, and moisture vapour transmission. Moreover, the current study provides a comprehensive overview, characterisation, and comparison of the critical properties of various wound dressings, which may assist researchers in developing innovative wound dressings.

A summary of all tested dressings is presented in Table 3.